While blood brain barrier (BBB) impairment is a critical feature of HIV-1 neuropathogenesis, the BBB also serves as a conduit for therapeutics brain delivery. How this intersects with BBB pathophysiology is the focus of the current project. It is a now well-established fact that neural progenitor cells (NPC) dynamically contribute to neuro- and gliogenesis in the postnatal brain and are being developed in this program grant (project 1, J. Zheng). In response to injury, infection, or neurodegeneration, progenitor cells migrate toward zones of tissue damage. Chemokines produced in association with neuroinflammatory responses likely act as chemoattractants for neural progenitors during brain injury. Whether NPC cross the BBB from blood remains unclear. We propose that systemic NPC can migrate across the BBB and promote neuroprotection while attenuating neuroinflammation in HIV-1 encephalitis (HIVE). We will study mechanisms governing NPC migration and their effect on the BBB using the pathophysiologically relevant assumption of chemokine overproduction in neuroinflammation. We will investigate how migration across the BBB alters how NPC differentiate into neurons and glia and the effects of NPC on the BBB from within the brain. Strategies in this program grant are being developed that enable a broad spectrum of anti-retroviral and adjunctive medicines for HIV-1 to be packaged into nanoparticles (NP; project 2, H. Gendelman). These can be taken by leukocytes and transported into areas of active neuroinflammation. While being an attractive specific way to facilitate anti-retroviral or anti-inflammatory drug delivery, it is currently unknown how NP-containing leukocytes affect BBB function during migration or from the 'brain' side of the barrier and perhaps even more importantly how they affect neuronal and glial integrity. Therefore, we will address the pathways and nanotoxicology for migration of macrophages across BBB with drug laden NP. We will evaluate the cell's ability to move and affect the integrity and function of the BBB and to affect diseaserelated neuropathology. These cell-based novel therapeutic approaches are interdisciplinary and show ynergy amongst the projects (NPC project 1, J. Zheng and NP-delivery of drugs project 2, H. Gendelman) with our own established expertise in BBB models. Importantly, three diverse animal models for HIVE will be employed to validate in vitro observations using in vivo imaging techniques allowing assessment of BBB integrity, neuronal injury, and neuroinflammation.